SportsTurf provides current, practical and technical content on issues relevant to sports turf managers, including facilities managers. Most readers are athletic field managers from the professional level through parks and recreation, universities.
Issue link: http://read.dmtmag.com/i/50965
FieldScience K in soil sampled from 0-6 inches. I understand managers of sand- based football fields are investigating lower mowing heights to pro- mote "shallow" root density and enhance divot resistance and stability of the playing surface. A clever tactic given lower mowing heights (within recommended ranges for a turfgrass species) corre- late to lesser mean rooting depths (all other things equal), but not less total roots! Like many superintendents managing annual blue- grass putting greens, these athletic field managers may constrain fer- tility assessment to the upper 4" of soil. But how can SLAN cope? Easily, the recreational turfgrass target of 250 lbs K/acre translates to 188 ppm K in 0-4" of soil. Thus, if analysis shows exchangeable K of 150 ppm soil, then optimal K fertility will require a 38 ppm soil K increase. The 0-4" deep acre root zone weighs 1.33 million pounds, thus a rectifying application of 51 lbs K (61 lbs K2O) per acre is recommended. To these scenarios application of BCSR theory generates an iden- tical recommendation, hardly as intuitive or meaningful as those shown. SUITABILITY BCSR-derived recommendations typically fail to optimize K availability in soils having limited cation exchange capacity (CEC). Considering SLAN effectively interprets fertility over a wide range of soils, suitability serves as yet another harbinger of doom for the BCSR–turfgrass relationship. For example, a 6" sand rootzone sam- posite is true. When the soil opens up physically and more air and water is moving through the soil biology is more active and the nitrification processes work better. We consistently see ath- letic field managers using less fertilizer and getting better vigor, color and recovery. The one input that we may shift for a year or two is the use of calcium products, if the soil test calls for that, as we bring the base saturation of calcium up to the 60 percentile mark. This may be the least expensive input in any program but the impact is significant. The calcium products are not exclusively designed to feed the plant but instead are used to flocculate the soil, opening it physically, and helping to stim- ulate soil biology which will in turn puts the plant into a posi- tion where nutrient mobility is improved. Once the soil is balanced chemically to allow for a better physical and biological profile the entire focus is sufficiency levels of nutrients so that we can assure that the plant is get- ting all that it needs especially at high stress times on the ath- letic fields. This approach makes sense, it addresses both the soil needs and the plant needs not just the latter. It has been proven in the field for years, over and over again, helping turf managers become more successful with less, reducing plant stress. This reduces the need for many inputs including fertil- izers and pest control products. The bottom line is if using base saturation models as a tool truly did not work, sports turf managers would not use it a 30 SportsTurf | January 2012 www.sportsturfonline.com